The International Olympic Committee (IOC) has stripped four more athletes — including three Russians — of medals from the 2008 Beijing Olympics after their doping samples were retested and came back positive.

The IOC says a total of six athletes were sanctioned on August 31 based on reanalysis of their samples with improved techniques.

Tatyana Firova of Russia was stripped of her silver medal in the women's 4x400-meter relay.

Russian weightlifters Nadezda Evstyukhina, who won bronze in the women's 75-kilogram category, and Marina Shainova, who took silver in the women's 58-kilogram, also tested positive for banned substances, as did Armenia's men's 69-kilogram silver medalist Tigran Martirosyan.

Two other weightlifters who did not finish in the top three in their events, Alexandru Dudoglo of Moldova and Azerbaijan's Intigam Zairov, were also named by the IOC.

The six are the latest in a series of athletes who have tested positive for forbidden substances in retests of samples from Beijing and the 2012 London Olympics.